textproduct: Quad Cities

KEY MESSAGES

- A Heat Advisory is in effect for areas mainly south of I-80 but also including the Quad Cities metro until 7 PM; expect peak heat indices in the lower 100s in this area. A Special Weather Statement has been issued just to the north and east of the advisory for peak heat indices between 95 to 100 degrees.

- Isolated to scattered (10-40%) showers and storms are expected this afternoon and evening. Isolated severe storms are possible, mainly south of I-80 with damaging winds being the primary risk.

- A very unstable air mass will develop on Monday with a notable increase in humidity compared to Sunday. This setup could support severe thunderstorms later in the day as a cold front moves in from the northwest. SPC has an Enhanced Risk (level 3 of 5) for severe storms northwest of the Quad Cities and a Slight Risk (level 2 of 5) to the east and south.

- Canadian wildfire smoke is forecast to spread across the area tonight through Sunday, which will likely lead to hazy skies and potentially to poor air quality.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 245 PM CDT Sat Jul 18 2026

A weak cold front will continue to shift southward through eastern Iowa and northwest/west-central Illinois this afternoon and evening, which could provide a focus for development of isolated showers and storms. Areal coverage of storms through late evening is anticipated to remain isolated to scattered, and most favored in counties south of I-80. With a hot and humid air mass in place there will be plenty of instability to work with (MLCAPE values reaching 1500-2500+ J/kg), especially along and south of I-80. Despite weak deep layer shear, a few strong to severe storms are possible with the main threats being localized damaging winds and heavy downpours. The main window for convection will be between 4 PM - 10 PM, with limited coverage for the rest of the night as a slightly less humid air mass advects in from the north. Lows tonight will be in the 60s.

For Sunday, expect a less humid day compared to conditions over the past week. It will still be very warm with highs in the mid/upper 80s but peak heat indices will only reach the mid 80s to lower 90s for most of the outlook area. The main story on Sunday will be the potential for degraded air quality as Canadian wildfire smoke moves in from the E/NE. Smoke aloft will result in hazy skies and we do anticipate a period of near surface smoke, which may lead to minor reductions in visibility and to poor air quality. An Air Quality Alert has been issued by the Illinois EPA for all of our Illinois counties from midnight tonight until midnight Sunday night.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 245 PM CDT Sat Jul 18 2026

Monday/Monday night Assessment...high (>80%) confidence on hot and humid conditions.

Hot and humid conditions will return again on Monday as southerly flow brings moisture back into the area ahead of an approaching cold front. Based on forecasted temperatures, heat indices and WBGT the probability is high (70-80%) that much of the area will need heat headlines.

The Storm Prediction Center has an Enhanced Risk (level 3 of 5) for severe storms northwest of the Quad Cities and Slight Risk (level 2 of 5) to the east and south. The primary risk looks to be damaging winds. The ECMWF EFI for CAPE- Shear is showing a notable signal, compared to mid summer climatology, for moderate/high instability and wind shear across our northern CWA (with values between 0.5 - 0.7), providing confidence on an environment supportive of severe thunderstorms. Timing of thunderstorms is uncertain at this lead time. There is potential for scattered activity Monday AM and then a more widespread round is possible Monday evening and night.

Tuesday through Thursday Assessment...high (>80%) confidence of a respite from the heat and humidity

After the passage of the cold front Monday, northwest flow aloft will dominate resulting in much less humid conditions and temperatures dropping to or slightly below normal.

There will be weak disturbances in the flow aloft moving through the area on a daily basis. However, moisture will be lacking so dry conditions are expected. However, that does not rule out the possibility of a rogue diurnal shower or storm developing during peak heating each day. The disturbance on Thursday looks to be the strongest of the three days. So, if there is sufficient moisture available, some isolated (10%) diurnal convection would be possible.

Friday Assessment...low (<25%) confidence on rain chances

On Friday the global models will drag another cool front through the area. Ahead of the front, return flow will bring moisture back into the area. The model consensus has a 20 percent chance of rain. However, the MJO will be stalling due to destructive interference with the dominate background El Nino state. At the same time the MJO will be in phase 7 or 8 which correlates to lower than normal chances for rain.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1258 PM CDT Sat Jul 18 2026

Isolated showers and storms are possible later this afternoon and evening, mainly south of I-80 with highest chances near BRL. Confidence remains low on areal coverage and exact timing, so have continued with PROB30s in the TAFs at MLI and BRL. Brief MVFR/IFR is possible in the vicinity of any showers/storms. Winds will turn predominantly to the NW/N this afternoon and evening.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Heat Advisory until 7 PM CDT this evening for IAZ067-068- 076>078-087>089-098-099. IL...Heat Advisory until 7 PM CDT this evening for ILZ015-024>026- 034-035. Air Quality Alert from midnight tonight to midnight CDT Sunday night for ILZ001-002-007-009-015>018-024>026-034-035. MO...Heat Advisory until 7 PM CDT this evening for MOZ009-010.